Go's garbage collector is exclusively stop-the-world, so it seems like this is going to die in a fire pretty quickly with a non-trivial heap size (more than 1GB). HotSpot's CMS collector (which is parallel & concurrent) has a pretty rough time with heaps >16G and it's been maturing for over a decade.
It's a function of the number of keys more than heap size directly. I've benchmarked the STW at 20ms pauses for ~2G if the values are ~10k each, and 200ms if the keys are 1K each at the same amount of RAM.
